The origin of puppy-dog eyes

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Scientists now know how man’s best friend got its puppy-dog eyes. The sad, soulful expression that turns dog owners into total pushovers is the result of tens of thousands of years of evolution and an eyebrow-raising muscle. To understand how the process of domestication shaped the modern pooch, researchers dissected the heads of wolves and dogs that had died natural deaths. They found that the musculature of the heads differed only in one key area: around the eyes. Unlike wolves, dogs have a small levator muscle that lets them raise their inner eyebrow, making the eye appear larger and more babyish. This, the researchers said, is evidence of evolution in action: In the early days of domestication, some 33,000 years ago, the wolves that could elicit the most sympathy from our Stone Age ancestors would have received the most scraps of food. Ancient canines with expressive eyebrows had an evolutionary advantage that they then passed on to their descendants. “We prefer dogs with these kind of infant-like large eyes,” co-author Juliane Kaminski, from the University of Portsmouth in England, tells The Times (U.K.). “We see this movement, this raised eyebrow, and it triggers a nurturing response. We want to take care of this thing.” ■